1. Field of the Invention
This invention relates to a retainer for bearing. More particularly, it is concerned with a retainer for bearing having a pocket in an oval shape.
2. Description of the Prior Art
A ball bearing has been, and is, of such a construction that, as shown in FIGS. 1 and 2 of the accompanying drawing, it has an inner ring 1, an outer ring 2, a ball 3 hold between the inner and the outer rings, and a retainer 4 with a pocket 5 for confining the ball within its inner surface.
An oil-lubricating or self-lubricating type retainer is made of a base material, either inorganic or organic (such as sintered alloy, plastics, etc.), which is impregnated with a solid lubricant like molybdenum disulfide, graphite, and others.
In actual use, the self-lubricating retainer 4 applies the solid lubricant to the surface of the ball 3 through the pocket surface of the retainer, thereby lubricating the rolling surfaces of the inner and outer rings 1, 2.
This type of the pocket 5 in the ball retainer 4 is formed in a true circle having a diameter greater than that of the ball 3.
Since such conventional retainer 4 having the pocket 5 in true circle requires a pocket clearance (a difference between the inner diameter of the pocket and the diameter of the ball) to be at a certain value or greater, the following inconveniences would take place.
(1) A contact area at a contact part 6 between the ball 3 and the pocket surface is small, hence a mean surface pressure at the contact part becomes high to result in considerable wear at that part.
(2) The small contact area between the ball 3 and the pocket surface causes decreased supply of the self-lubricant from the retainer to the rolling surface of the ball 3 with the consequent increase in frictional resistance.